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My computer appears to be assigned a subnet ip address from my isp's router and I do not actually have my own ip address. Is this possible through network address translation or NAT?

I have wanted to host a website for a little while now, but I do not think I can using what ever ip address my packets appear to come from (which I think would be my router or gateway) because either the ISP does not want to be a server, or it simply doesn't know to whom on the subnet; to route the packets. Just to be painfully clear, say my ip address (or gateway's ip address) was 233.234.92.3 (I just made that up). If I linked my domain name to that ip address, the gateway I am on would have no way to know where to route the packet on the subnet it is connected to.

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  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Aug 12, 2017 at 19:12

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If I linked my domain name to that ip address, the gateway I am on would have no way to know where to route the packet on the subnet it is connected to.

Let's recap what you've described: the gateway here has a public-Internet-facing IP address (the one you see when you visit WhatIsMyIP?). It also has a private-subnet-facing IP address. The gateway does network address translation (NAT): it translates the (public, shared) destination IP address in incoming packets to the private IP address of a host on the subnet, and it translates the private source address of outgoing packets from hosts on the subnet to the public IP address of the gateway, which is shared by all hosts on the subnet.

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(Image source: FileZilla Wiki, licensed under GNU Free Documentation License 1.2)

You've correctly noted that in most cases, a NAT can forward outgoing traffic, and receive incoming traffic for established sessions (that's how you can receive data back once you contact a website, for example), but it doesn't know how to forward incoming traffic for new sessions.

The solution to this particular problem is NAT "port forwarding" or "port mapping." To use this, you would define port forwarding rules on your NAT device (e.g. router) that say, for example, "Packets received on TCP port 80 should be forwarded to 192.168.0.44."

(You may face other problems that are not solved by port forwarding, however. For example, if you haven't paid for a static IP address, your ISP may change the public IP address assigned to your gateway whenever it feels like it, which will break your setup.)

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There seems to be a lot of confusion in your question. Let me see if I can untangle some of it.

  1. The IP address you made up is actually in the multicast address range. Currently those are not routed over the Internet. Ignoring that for the moment:

  2. You could, in theory set up a web server on your network. Your ISP may have policies to prevent that, but from a networking perspective, it will work fine. Your gateway already knows how to route packets to your host. Otherwise how could you browse the web? (i.e., How would all those funny cat videos get to you?)

  3. You can ignore this for the moment, but it's highly probable that your host is behind a router that is performing Network Address Translation, or NAT. You can read more about that, but briefly the router translates your IP address from a private one to one assigned by the ISP. This is usually done dynamically. You will need to set up a static translation.

  4. It appears that you're hung up on the idea of "subnets." Subnets are just networks. From a routing perspective, "networks" and "subnetworks" are the same thing.

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  • So there is a way, that helps. But I'm still confused because if I go to a website that tells me what my ip address is, and use that ip address on godaddy or something to point the domain name to it, it fails except for client's on the subnet.
    – marshal craft
    Oct 12, 2015 at 16:16
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    There are several possibilities. Is your host IP (as reported by the host) the same as the one reported by "WhatismyIP"? If not, then you need to deal with #3 above. If yes, perhaps your host has a firewall that does not allow incoming connections. Perhaps your ISP is blocking port 80 connections because they don't want people like you to run web servers on residential accounts. For more information on how to set up a web server, you should ask on Superuser.com. Home networking questions are off-topic here.
    – Ron Trunk
    Oct 12, 2015 at 17:13

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